Sound translating device



INVENTOR. Fllber E. [111m: druff BY M kJ/ww ATTORNEYS.

May 6, 1941. A'. E. WOODRUFF lSOUND TRANSLATING' DEVICE Filed May 26, 1938 Patented May 6, 1941v UNlTaD STATES PATENT oFFlcE #,ZQLIW v'Albert n. Woodruff, oak ruk, n1., mmf to Associated Electric Laboratories, Inc., Chicago, lli., a' corporation of Delaware Application May 26, 19.38, Serial No. 210,179

2 Claims. (Cl- 179-119) In general, the objects as set forth above are attained in accordance with the present inven- Y The present invention relates to sound translating devices and more particularly to a magnetic unit adapted to be utilized in a telephone transmitter or receiver.

In a sound translating device a magnetic unit is provided which conventionally comprises a field structure including a substantially U-shaped permanent magnet having two outwardly extending legs, each of which is individually associated with two spaced-apart pole pieces formed of magnetic material. The pole pieces are arranged in two sets, the pole pieces of each set being directed toward each other, and the pole faces ofeach set of pole pieces being arranged in spaced-apart relation in order to receive therebetween the opposite ends of a pivotally mounted armature formed ofl magnetic material. One end oi the pivotally mounted armature is yconnected to a diaphragm, and a winding or voice coil carried by a winding spool arranged between the two sets of pole pieces is electromagnetically coupled to the armature. In the case of a telephone transmitter, the vibrations of the diaphragm, produced bythe sound to be transmitted, cause the ends of the armature to vibrate between the pole faces of the two sets of pole pieces, thereby to generate a corresponding signal voltage. In the case ofa telephone receiver, the signal current passing through the voice coil causes the ends of the armature ,to vibrate between the pole faces of the sets of pole pieces, thereby to reproduce at the diaphragm a corresponding sound. The field structure of a magnetic unit of thistypeis usually carried by a supporting plate, one leg ofthe permanent magnet being arranged in abutting engagement with the plate and secured thereto. Also, the magnetic unit is provided with an enclosing casing secured to the'supportlng plate in order to exclude dust and moisture therefrom. While a magnetic unit of type is satisfactory in operation, it requites a larger enclosing casing and is of larger size"than is desirable.

Accordingly, it ls an object of the present invention to provide, in a sound translating device, an improved magnetic unit of the type described which is of compact and rugged construction, and which embodies an enclosing casing of relatively small size.

- Another object of the invention is to provide, inl` a soundY translating device, a magnetic unit ofthe type described which includes a field structure and a supporting plate, and which embodies Y an improved arrangement for mounting the field structure on the supporting plate.

tion by providing, in a Isound translating device,

a magnetic unit of the character noted comprising a field structure including two outwardly extending eld members arranged in spaced relation, pole pieces carried by the field members which are directed toward each other and arranged in spaced relation-in order to receive therebetween a movable armature, a supporting element provided with an outwardly extending recess therein, one of the iiel'd members being arranged in the recess in the supporting element in order to reduce the distance between the other field members and the supporting element, and means for securing the field structure to the supporting element,

In accordance with another feature of the inventionI the eld structure comprises a U-shaped 4 'tially U-shaped field element having two legs arranged in spaced relation, corresponding legs on the eld elements being directed toward each other and constituting pole pieces arranged in two sets. Means are provided for securing the eld elements together with the pole faces of each of the sets of pole pieces arranged in spaced relation and for securing the ileld elements to the supporting element adjacent the recess there- A winding spool is arranged between the two sets of pole pieces and carries an armature plvotally mounted' thereon, the opposite ends of the armature being arranged between the pole faces of the two sets of pole pieces. Oneof the legs of the U-shaped magnet is arranged in the recess in the supporting element in order to reduce the distance between the other leg of the magnet andthe supporting element. An enclosing casing is provided for the magnet unit which is secured to the supporting element, one wall of the enclosing casing being arranged closely adjacent the other leg of the U-shaped magnet.

Thenovel features believedto be characteristie of the invention are set forth with particularity in the appended claims. The invention, s

both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specication taken in connection with the accompanying drawing in which Figure 1 is a side elevational view, partly in section, of a magnetic unit for a sound translating device and embodying the present invention; Fig.

another set.

A2 is an end elevational view, partly in section, of the magnetic unit of Fig. 1; Fig. 3 is an enlarged plan View of a portion of a winding spool and armature assembly embodied in the magnetic unit; and Fig. 4 is a sectional view of the complete assembly taken along the line 4 4 of Fig. 3. 'Hiili Referring now more particularly to Figs. 1 and 2 of the drawing, there is illustrated a magnetic unit I0, adapted to be utilized in a sound translating device in the form of a telephone transmitter of the sound-powered type or a telephone receiver, which comprises a magnetic eld structureincluding a substantially U-shaped permanent magnetII having two outwardly extending field members or legs I 2 and I3 arranged in spaced relation, and two substantially U-shaped field elements I4 and I5 formed of magnetic material. The eld elements I'4 and I5 are each provided with two leg's I 6, I1 and I8, I9, respectively, arranged in spaced relation, corresponding legs on the field elements 'being directed toward each other and constituting pole pieces arranged in two sets. The pole pieces I8 and I8 constitute one set andthe pole pieces I1 and I9 constitute 'I'he field elements I4 and I5 are provided withoutwardly extending lugs 20, 2I and 22, 23, respectively, and aresecured together with the pole faces of each set of the pole pieces arranged in spaced relation by an arrangement comprising two bushings 24 and 25 arranged between the lugs 20, 22 and 2|, 23, respectively, and two screws 26 and 21 extending through aligned openings formed in the lugs and bushings. The screw 26 extends through aligned openings formed in the lugs 20 and 22 and the bushing 24; and the screw 21 extends through aligned openings formed in the lugs 2 I, 23 and the bushing 25. The outer ends of the screws 26 and 21 are arranged in threaded engagement with openings provided in a supporting element or plate 28, thereby securely to retain the field structure to the plate 28.

The leg I2 of the magnet II engages the ield element I4 and is secured thereto by an arrangement comprising a strap 29 embracing a portion of the leg I2 adjacent the outer end thereof, the

opposite ends of the strap 29 being clamped be- A tween the` heads of the screws 26 and 21 and the adjacent lugs 20 and 2I, respectively, on the field element I4. Preferably, the opposite ends of the strap 29 are provided with openings therein, through which the screws 26 and 21 extend. The leg I'3 of the magnet II engages the eld element I and is secured thereto by a screw 30 exten-ding' through an opening formed in the leg I3- and threaded into an opening formed in the eld element I5. The plate 28 is provided with an-outwardly extending recessA 28a therein which receives the leg I3 of the magnet II, the inner surface of the leg I3 engaging the adjacent surface of the field element I5 and being arranged substantially in the plane of the inner surface of the plate 28. This arrangement substantially reduces the distance between the inner surface of the plate 28 and the outer surface of 3 and 4, comprises a winding spool 32 formed of insulating material such as Bakelite and an armature 33 formed of flat magnetic stock.

The winding spool 32 is split longitudinally and comprises complementary upper and lower sections 32a and 32h, respectively, of similar construction. Each'of the sections includes a body portion 34 carrying two spaced-apart winding retaining heads 35. The wall of the body 34 of the lower section 32b is provided with a longitudinally extending recess 34a therein which is disposed adjacent the joint between the upper and lower sections 32SL and 32h, respectively. The wall of the body of the upper section 32a is substantially flat adjacent the joint between the upper and lower sections 32 and 32h, respectively. The armature 33 is provided with a longitudinally extending operating lug 36 and two transversely extending spaced-apart lugs 31 intermediate the ends thereof. Each of the lugs 31 projects from one side of the armature 33 and is provided with a head 31a connected by a length 31b to the armature 33, the length 31b being of reduced cross-sectional area. 'The armature 33 is arranged in the recess 34 provided in the wall of the body 34 of the lower section 32h, the arma- `ture 33 being retained imposition by spacedapart and aligned recesses 34b provided in the body 34 of the lower section 32b and receiving the heads 31a on the lugs 31. The lugs 31 are retained in the recesses 34b provided in the body 34 of the lower section 32b by two mounting clips 38. Each of the clips 38 is of substantially U-shape comprising two flanges 39 and 40, the flange 40 being provided with three spacedfapart fingers 40, 4l]b and 40C. Each of the clips 38 embraces one side of the body 34 of the lower section 32h, the c1ip'38 being retained in place by the clamping action between the two outside fingers 4I)a and 40C, and the flange 39 upon the body 34. The intermediate finger 40b on the clip 38 engages the head 31 on one of the lugs 31, thereby rigidly securing the lug to the body 34 of the lower section 32h. 'Ihe clips 38 mount the armature 33 on the body 34 of, the lower section 32b for vibratory movements about an axis extending between the lugs 31 transversely of the winding spool 32.

In constructing the assembly 3 I, the armature 33 is brought into position with respect to the recesses 34b provided in the body 34 of the preformed lower section 32D of the winding spool 32 and'lowered into place, the hea-ds 31 on the lugs 31 being received in the recesses 34b formed in the body 34, The clips 38 are then placed upon the sides of the body 34, and the outside lingers 4I]8L and 40c and the ange 39 are bent into engagement with the vbody 34 in order securely to fasten the clips 38 thereto. The armature 33 is then aligned and the intermediate fingers 4Gb are then bent in-to engagement with the heads 31a on the lugs 31 in order securely to retain the armature 33 in position. ,The preformed upper section 32a is then brought into superimposed relation with the lower section 32h to complete the assembly 3|, the upper and lower sections 32aL and 32h, respectively, being retained together by the eld structure of the magnetic unit in any suitable manner.

The walls of the body 34 of the upper and lower sections 32a andl 32!l are spaced a short distance from the armature 33, and the ends of the armature 33 project through the winding spool 32.

these ends of the armature being protected f against injury by projections 42 provided on the ends of the sections 32a and 321. Thus, the comis provided with a' wall surrounding a narrow openingl extending longitudinally therethrough,

the armatin'e 33 being arranged within the opening in the body. The amature 33 is supported by the lugs 31 for vibratory movements out of contact with the wall of the body and about an axis extending between the lugs 3'I transversely of thewinding sp'ool 32. When the amature 33 is moved from its normal position, the lugs 31 are subjected to torsional strains, these strains being localized in the lengths of reduced cross-sectional areas .31 of the lugs 31. This torsional mounting of the armature 33 is very advantageous as it causes the armature to be deflected an amount of the leg I2, the pole piece I3 of the iield element Il, the amature 33. the pole piece I! of the field element I l and the leg I3 to the south pole of the permanent magnet II. On the other hand, when the amature is moved in a counterclockwise directionabout its pivot, the magnetic field of the i-leld structure traverses a path extending from the north pole of the permanent magnet Iiby precisely corresponding to the force exerted on the operating lug 3l, the deiiection of the armature 33 being directly proportional to the force exerted upon the operating lug 3i over a wide range. i

A winding, not shownjis arranged about the body 3l between the winding retaining heads 35' of the winding spool 32 and one endv 33 of the armature 33 is-disposed between the oppositely diseposed polefaces of the set of adjacent pole pieces I1 and i3, while the other end 33b of the amature 33 is disposed v,between the oppositely Y adisposed' pole faces of the setl of adjacent pole pieces I3 and I3. 'I'he operating lug 33 on the armature I33 is provided with an opening therein in which one end of a rod eis secured, the rod 43 extending through an opening formed in'the leg I3 ofthe magnet II. 'I'he otherv end of the rod I3 is secured to a soundwave-responsive diaphragm 44 by an arrangement comprising a pair of nuts Me. The periphery of the diaphragm 44 A is clamped between the outer surface of the supporting plate2ii` and an annular ring 45 secured to the plate 28. Anarrangement comprising a moisture-proof washer 43 interposed between the diaphragm Il andthe supporting plate 23 and a moisture-proof washer 41 interposed between the diaphragm 44 and the ring 45 is provided for sealing the interior of the casing of the magnetic unit against the entrance of dust and moisture thereinto. The magnetic unit is also provided with an enclosing casing 48 which is secured to the. supporting plate 28 by an arrangement comprising an annularV ring 49, which eifectiveiy seals the interior of the casing vof the magnetic unit against the entrance of dust and moisture thereinto.

l l ture including two ileld elements secured together' A and provided with cooperating pole pieces, a piv- Normaliy, the amature 33 occupies a position y wherein 4the opposite ends thereof are disposed intermediate the adjacent pole facesvof the two sets of pole pieces and is'adapted to be vibrated therebetween. When Vthe magnetic unit is utilized in a telephone transmitter of the soundmoved. in a clockwise direction about its pivot, as viewed in Fig. 1, the magnetic field of the iield structure traverses a path extending from-the north pole of the pennanent magnet Il by way the transmitted sound. 'As the armature 3': is

.way ofthe leg I2, the pole piece Il of the field duringl the vibratory movement of the amature- 33, 4the magnetic field of the field structure traverses the armature. 33 in opposite directions; in a well-known manner. V

Due to the arrangement of the leg I3 of the magnet II in the recess 28 in the supporting plate 23, the distance between-the inner surface of the supporting plate 23 and the outer surfacel of the leg' I2 of the magnet I I. is substantially reduced. thereby effecting a considerable reduction in the over-all height of the magnetic unit. Due to this reduction in the over-all height of the magnetic unit, the enclosing casing I8 thereof may be constructed considerably smaller and the inner wall thereof may be arranged closely adjacent to the outer surface of the leg I2 of the magnet I I without interfering with the operation of the magnetic unit. Moreover, the particular arrangement for securing the iield elements Il and I5 in spaced-apart relation and to the supporting plate 28, and the arrangement for securing the magnet -l Into the field elements Il and I5 are very'advantageous, as they render the magnetic structure of rugged and compact construction. Finally, these arrangements embodied in the magnetic unit are productive of substantial manufacturing economies.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood thatvarious modi'cations may be made therein, and it is contemplated to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a sound translating device, a field strucotally mounted armature operatively associated with said pole pieces, a substantially U-shaped magnet'having two outwardly extending legs arranged in spaced relation and embracing said iield structure, means for securing the legs of said magnet to said field structure, thereby to support said magnet, a supporting plate having a slot provided therein, said ileld structure being arranged adjacent the inner side of said supporting plate, whereby one ofsaid eld elements overlies the slot provided therein, means for securing said one field element to the inner side of said supporting plate on opposite sides of the slot provided therein, thereby tosupport said field stmoture, one of the legs` of said magnet and the inner side of said supporting plate being arranged in spaced relation and the other leg of said magnet being arranged in the slot provided in said supporting plate, thereby to minimize the distance between the one leg, ofrsaid magnet and the inner side of said supporting plate, and a casing secured to said supporting plate and enclosing said eid structure and said magnet, said casing having an end wall arranged closely adjacent the one leg of said magnet.

2. I n a sound translating device having a diaphragm. a eld structure including two eld elements secured together and provided with cooperating pole pieces, a pivotally mounted armature operatively associated with said pole pieces,

a substantially U-shaped magnet having two out--4 wardly extending legs arranged in spaced relation and embracing said eld structure, thereby to support said magnet, a supporting plate having a slot provided therein, said field structure being arranged adjacent the inner side of said supporting plate, whereby one of said field elements overlies the slot provided therein, means for securing said one field element to the inner side of said supporting plate on opposite sides of the slot Provided therein, thereby to support said field structure, one of the legs of said magnet and the inner side of said supporting plate being arranged in spaced relation and the other leg of said magnet being arranged in the slot provided in said supporting plate, thereby to minimize the distance between the one leg of said magnet and the inner side of said supporting plate, and a link passing through a. hole in said-other leg connecting the armature and the diaphragm.

ALBERT E. WOODRUFF. 

